The basis of mutant phenotypes in membrane-associated traits of cultured mammalian cells will be investigated in genetic, biochemical, and immunological experiments. Human cells resistant to ouabain inhibition of plasma membrane Na/K transport ATPase will be examined with respect to K ion transport, ouabain binding, surface antigens, molecular properties of the ATPase, and expression of the traits in somatic cell hybrids. Chinese hamster ovary (CHO) cells resistant to Concanavalin A and temperature-sensitive for growth will be studied to determine the membrane-associated alterations and to analyze the markers in somatic cell hybrids. Other experiments will be undertaken to detect variant cells resistant to antibody and complement cytotoxicity, and to assess the prospects for detection of mitotic recombination in cultured cells. BIBLIOGRAPHIC REFERENCES: Baker, R.M. Genetics of Quabain-resistant mutants. Society of General Physiologists Symposium on Biogenesis and Turnover of Membrane Molecules, Woods Hole, Sept., l975. Raven Press, New York, in press. Baker, R.M. and V. Ling. Membrane mutants of mammalian cells in culture. METHODS IN MEMBRANE BIOLOGY (ed. E. D. Korn), Vol. 6, Plenum Press, New York, l976, in press.